I have a sister through nursing (breast feeding), is it permissible for me to marry her younger sister?

"The question is ambiguous, but sharing breastfeeding with the mentioned girl has three possibilities: either she was breastfed by your mother, or you were breastfed by her mother, or you both shared breastfeeding from a woman who is not the mother of either of you. In the first and third possibilities: the prohibition does not extend between you and her sister, and therefore it is permissible for you to marry the younger sister of your sister through breastfeeding if no other reason for prohibition between you is established. But if the girl's sister is a sister to you through breastfeeding because you were breastfed by her mother or by her father's wife from his milk: then the mentioned girl is a sister to you through breastfeeding if the breastfeeding reached five satisfying feedings according to the most correct opinion.

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